Rendezvous Concept Research Articles

Interdisciplinary rendez-vous approach in endovascular stroke treatment a new concept to accelerate mechanical thrombectomy in primary stroke centers

Abstract Background/Introduction Prompt endovascular treatment of patients with stroke due to intracranial Large Vessel Occlusion (LVO) is a major challenge especially in rural areas because neurointerventionalists are usually not available. As a result, treatment is delayed, and clinical outcomes are worse compared with patients primarily treated in comprehensive stroke centers (CSC). Purpose To address this problem, we present a new concept in which interdisciplinary, on-site endovascular treatment is performed in a Primary Stroke Center (PSC) by a team of interventional cardiologists and neuroradiologists: the Rendez-Vous approach. Methods Twenty-seven patients with LVO who underwent interdisciplinary thrombectomy on-site at the PSC as part of the Rendez-Vous concept were compared with 72 patients who were transferred from a PSCs to the CSC for thrombectomy when diagnosed with LVO in terms of temporal sequences and clinical outcomes. The crucial aspect of the concept is that the patient is not transferred for the intervention but is treated on site and the cardiologist actively starts the intervention while the neurointerventionalist rushes to the site as soon as possible. Results Patients treated on-site at the PSC as part of the Rendez-Vous approach were managed as successfully and without an increase in complication rates compared with patients treated secondarily at a CSC (91.7% successful interventions in Rendez-Vous vs. 87.3% in control group, p=0.57). The time from diagnosis of LVO to groin puncture was reduced by 68.3 minutes with the Rendez-Vous concept (p<0.01). Regarding the clinical outcome, a functionally independent status was achieved in 37.0 % in the Rendez-Vous group and in 19.4% in the control group (p=0.012). Conclusion Interdisciplinary teamwork between cardiology and interventional neuroradiology in rural PSCs leads to shorter times to successful reperfusion in patients with severe ischemic stroke due to LVO. This has a potentially positive impact on the clinical outcome of stroke patients and should be considered as a possible care concept in similar stroke networks.Rendez-Vous concept in stroke management

Employee Engagement, Organizational Intimacy and Talent Management: A Common Buzz Phrase in the Human Resource Development

Major changes have become a part of the business practices for most of the organizations due to tough competition for most of the organizations. This is the ultimate reason behind the frequent demand for the changes. For both organizational behavior and human resource development, concerns have been increasing for employees. This has also become very important for making strategic decisions. It also helps to gain sustainability along with fulfillment of goals. Showing importance to employees also encourages the concept of employee rendezvous, organizational familiarity and talent management. This work aims to find more in-depth concepts of Employee engagement, organizational intimacy and talent management as well as association among them.

Trajectory Design of Perseus: A CubeSat Mission Concept to Phobos

The Martian satellites Phobos and Deimos hold many unanswered questions that may provide clues to the origin of Mars. These moons are low Δv stopover sites to Mars. Some human missions to Mars typically identify Phobos and Deimos as staging bases for Mars surface exploration. Astronauts could base initial operations there in lieu of repeated voyages to and from the planet surface, to refuel transiting spacecraft, to teleoperate robotics and other critical machinery, and to develop habitable infrastructure ahead of human landings. Despite their strategic and scientific significance, there has been no successful dedicated mission to either moon. For this reason, we propose Perseus, a geological imaging CubeSat mission to Phobos. Perseus, a 27U, 54kg CubeSat will return thermal and visible images at resolutions better than currently available over most of Phobos’ surface. This includes visible images at 5m/pixel and thermal images at 25m/pixel of Phobos’ surface. The Perseus mission is nominally intended to be a co-orbital mission, where the spacecraft will encounter Phobos on its Martian orbit. However, a hyperbolic rendezvous mission concept, to image Phobos on a hyperbolic flyby, is also considered to reduce the risks associated with orbit capture and to reduce mission costs. This paper presents the preliminary feasibility, science objectives, and technological development challenges of achieving these science goals. We then formulate two rendezvous concepts as a series of three nonlinear optimization problems that span the design tree of mission concepts. The tree’s root node is the heliocentric cruise problem, which identifies the near-optimal launch and arrival windows for the Perseus spacecraft. The leaf nodes of the design tree are the two rendezvous concepts that identify near-optimal co-orbital and hyperbolic trajectories for Phobos’ reconnaissance. The design problems are solved using evolutionary algorithms, and the performance of the selected mission concepts is then examined. The results indicate that a co-orbital encounter allows about one encounter per day with about 6 min per encounter. The hyperbolic encounter, on the other hand, allows a single encounter where the spacecraft will spend about 2 min in the imaging region with respect to Phobos. The spacecraft will obtain higher resolution images of Phobos on this feasible region than have ever been seen for most of the surface. These detailed images will help identify candidate landing sites and provide critical data to derisk future surface missions to Phobos.

Fast rendezvous profile evolution: From ISS to lunar station

Recently, the fast rendezvous profile trend is observed in the manned spaceflight domain. Since 2012, docking of 28 Russian vehicles (18 of them were Soyuz crew vehicles) has been accomplished using the 6-h and 4-orbit rendezvous profile. The heritage and the return of experience from those flights made possible to develop and implement a two-orbit rendezvous with an unmanned Progress vehicle in 2018 that demonstrated the feasibility to develop and fly a fast rendezvous with Soyuz in 2020. The fast rendezvous profile will bring the crew vehicle to docking point in just 3 h after the insertion into orbit. Furthermore, in the future an ultrafast (one-orbit) rendezvous profile is considered as well. Crew comfort on the way to the ISS is just one of the advantages of the fast rendezvous profile which will also be required to develop the double-launch approach for the transfer to a lunar station. Since the double-launch approach considers separate launches of the crew vehicle and the upper stage, this allows arranging an effective traffic toward the Moon using launch vehicles of lower capacity. Launches at different times will allow the crew vehicle to wait for a successful launch of the upper stage while being docked to the orbital station, and that will give much higher reliability of the double-launch scenario. In the future, double-launch scenarios which include visiting an orbital station could be applied to reusable spacecraft transit from the orbital station to the lunar station and back. Fast rendezvous is especially favorable for double-launch scenarios because of the upper stage's limited lifetime if fueled with low boiling point propellant components. The paper reviews the evolution of the fast rendezvous profiles which were initially used in the ISS program for further utilization of this experience for development of rendezvous concepts in double-launch scenarios for missions to a lunar station.

Towards modelling and analyzing timed workflow systems with complex synchronizations

Nowadays, workflow systems are becoming very complex, involving time constraints, priorities on tasks as well as elaborated synchronization schemes. As a result, the specification and the verification of such systems are demanding much theory to prove their correctness and determine their qualitative and quantitative properties. In this paper, we mainly deal with complex synchronization on timed workflow systems. To address this issue, we redefine the concept of rendezvous as a mechanism to synchronize time constrained concurrent tasks of different privileges (Master, Slave). We discuss the different strategies that a rendezvous can follow, and hence we determine all the synchronizations patterns that could be considered in specifying its behaviour. From there, we deduce 36 generic synchronization rules that can be associated with the concept of rendezvous. Based on this theory, we extend the Time Petri Nets formalism to the concept of rendezvous to introduce the RTPN model (Time Petri Nets with rendezvous). Then, a subclass of RTPNs called Time Workflow-nets with Rendezvous (RTWF-nets), are defined for the modelling and the analysis of timed workflow systems. Finally, a case study is addressed to show how our framework can deal efficiently and elegantly with complex synchronization requirements.

Cooperative control feedback: On backoff misbehavior of CSMA/CA MAC in channel-hopping cognitive radio networks

Due to dynamic channel availability in cognitive radio networks (CRNs), rendezvous problem is known as the most challenging issue in the design of media access control (MAC) protocol, which is a key step for secondary users (SUs) to start communication. With the concept of blind rendezvous, numerous channel-hopping sequence (CHS) based rendezvous schemes have been proposed to solve this problem in these years. Currently, little attention is paid to the design of a carrier sensing multiple access/collision avoidance (CSMA/CA) MAC based on these rendezvous schemes and also the rendezvous de-synchronization problem brought by multiple rendezvous networking paradigm into MAC design. To this end, we propose a cooperative channel-hopping based CSMA/CA MAC (named CoCH-CSMA/CA MAC) which works on the top of existing CHS based rendezvous schemes. Resulting from the rendezvous de-synchronization problem, a new type of collision, named false collision, is identified. As a SU cannot discern the false collision by itself, we design a cooperative control feedback scheme which employs correlation-based signal detection to reduce the coordination overhead of cooperation and helps SUs to avoid backoff misbehavior. Moreover, we analyze the behavior of our MAC protocol and its advantage. Extensive simulations prove that the cooperative control feedback scheme can effectively alleviate the impact of rendezvous de-synchronization problem on backoff misbehavior and improve network performance.

Sp806 Successful Blunt Recanalization of an Oblitrated Long Esophageal Stricture by Endoscopic Rendezvous

Esophageal strictures develop in up to 4% of individuals receiving head and neck radiation and in excess of 20% with concomitant use of chemotherapy. While complete obliteration is rare, it is an appreciated entity with few traditional therapeutic options. Frequently these individuals suffer a significant decline in their quality of life, abandoning use of their esophagus. In response, Van Twisk first described the concept of endoscopic rendezvous in 1998. In such a procedure the esophageal stricture is simultaneously approached from both the antegrade and retrograde directions.

Concurrency State Models and Java Programs

Concurrency State Models and Java Programs

Information rendezvous

This paper proposes a new type of asynchronous group communication tool called an information rendezvous system. The purpose of the system is to mediate between producers and consumers of information. Among other attributes, information rendezvous systems rely on the knowledge of the user community in determining the relevance of information. We also two describe two prototypes that demonstrate the feasibility of the information rendezvous concept.

Modelling the semantics of multitasking facilities in Concurrent C using Petri nets

Concurrent C (ConcC) [1] is a relatively new language that extends the C programming language [2] by incorporating multitasking facilities. These facilities are mainly based on the bidirectional rendez-vous concept, and they offer flexible and efficient mechanisms for the specification of concurrency, communication and synchronization often required in real-time systems. However, as for most real-time and concurrent programming languages such as Ada [3], the description of multitasking facilities in ConcC is lacking a rigorous and formal semantical definition. Most existing introductory materials to ConcC by its authors are informally described, and cannot be easily understood. In this paper, we explain the semantics of multitasking facilities in ConcC using the Petri net model. As is well known, the Petri net model is a formal graphical model that can describe concurrent behaviours of systems in a natural and intuitive manner, and yet it is based on strong mathematical and semantical foundations. Timed, inhibitor arc and predicate Petri nets are extensions that are used to enhance the expressive power of the basic Petri net to model and explain all ConcC multitasking features.

Rendezvous facilities: Concurrent C and the Ada language

The concurrent programming facilities in both Concurrent C and the Ada language are based on the rendezvous concept. Although these facilities are similar, there are substantial differences. Facilities in Concurrent C were designed keeping in perspective the concurrent programming facilities in the Ada language and their limitations. Concurrent C facilities have also been modified as a result of experience with its initial implementations. The authors compare the concurrent programming facilities in Concurrent C and Ada and show that it is easier to write a variety of concurrent programs in Concurrent C than in Ada.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Concurrent C

Concurrent programming is becoming increasingly important because multicomputers, particularly networks of microprocessors, are rapidly becoming attractive alternatives to traditional maxicomputers. Effective use of such network computers requires that programs be written with components that can be executed in parallel. The C programming language does not have concurrent programming facilities. Our objective is to enhance C so that it can be used to write concurrent programs that can run efficiently on both single computers and multicomputers. Our concurrent programming extensions to C are based on the rendezvous concept. These extensions include mechanisms for the declaration and creation of processes, for process synchronization and interaction, and for process termination and abortion. We give a rationale for our decisions and compare Concurrent C extensions with the concurrent programming facilities in Ada. Concurrent C has been implemented on the UNIX system running on a single processor. A distributed version of Concurrent C is being implemented.

Multiprocessor Implementations of Tasking Facilities in ADA

This paper analyzes the efficiency problems related to the implementation of the ADA tasking facilities on monoprocessor and multiprocessor systems. Three different implementations of the basic communication mechanism in ADA - the rendezvous concept - are discussed and compared. The implementation approach is the same in the three cases and it consists of translating the ADA parallel constructs into procedural calls to kernel primitives. The kernel primitives corresponding to the most complex implementation are described.

The rendezvous and monitor concepts

The efficiency of Ada's rendezvous concept is compared with Concurrent Pascal's monitor concept. The differences between the two approaches, as well as a number of issues relating to their implementation, are presented. The results indicate that a concurrent programming language should provide both types of concepts.

Operations and Functions of the Apollo Guidance Computer During Rendezvous

The Lunar Orbit Rendezvous concept of two manned spacecraft is a critical activity in the success of a lunar-landing mission. In present and future Apollo flights the command module and the lunar module are both equipped with an on-board capability to enable the crew to effect and complete a rendezvous. This on-board capability is centered around the Apollo Guidance Computer which receives inputs from the crew, as well as information from other on-board subsystems, to perform the guidance and navigation computations necessary to control the intercept.The purpose of this paper is to describe the operational functions performed by both spacecraft computers, their design, program organization, control options, displays, inputs, and crew interfaces. A time history of the operations and procedures used by the crew, and the computer's role, in each vehicle during rendezvous is discussed, as well as presentation of the results obtained by the on-board system for actual flights.